How do viruses form? Since the coronavirus has been all over the news, I've been wondering this question for a long time. - Samantha, 12, N.C.

Viruses are strange things. They’re not alive like you or me. But they behave somewhat that way—spreading, growing, appearing in new forms. How can this be?

There’s a lot scientists don’t know yet about the new coronavirus. But they do know a lot about how viruses work and make people sick.

To learn more, I talked to Sylvia Omulo, a scientist specializing in infectious diseases at Washington State University.

Your body is made of tiny building blocks called cells. Different cells do different types of work. They all follow instructions written in your body: your genes.

Viruses also have genes, but they don’t have cells like you or me. Instead, they rely on other creatures’ cells to come “alive.”

“A virus is a particle of genetic material that causes an infection by invading a cell,” Omulo explained. “It’s extremely small, smaller than a cell.”

You can think of a virus particle like a letter with bad news, tucked inside an envelope. Layers of protein (the envelope) cover a bundle of genes (the letter), protecting it until it’s ready to be opened and read.

Virus particles spread through the air or on surfaces. They cause infections if they get inside someone’s body. The envelope opens if the virus enters a creature’s cell, called the “host.” The virus uses its genetic instructions to take over the cell.

The virus disrupts the cell’s usual work, Omulo said, using its resources to make copies of itself. Those virus copies invade other cells, repeating the process. The host becomes sick as a result.

Usually, the virus copies itself exactly. But because viruses have genes, they also evolve over time. This means they’re changing, even as they’re making copies of themselves. That’s part of how new virus forms emerge.

Viruses have been around for millions of years, much longer than humans. Some only affect plants or bacteria. Some affect only some animals.

Other viruses spread from animals to humans. Omulo explained this is one way “new” viruses appear. A virus might affect humans, but not the animals carrying it. If it gets the opportunity to jump to humans, it can make them sick.

But remember: a virus isn’t alive on its own. It needs an opportunity to enter a cell. It’s your job to ruin that opportunity.

When you wash your hands with soap, you rub off the virus’s “envelope.” The bad news can’t go anywhere. When you keep distance from others, you close your “mailbox.” Virus particles can’t enter your cells or anyone else’s.

Without a host, a virus can’t do anything. That’s why it’s so important not to give the virus that chance.